Method of making permanent magnets



Z was it 29, 1935 UNITED. TATES METHOD OF MAKING PERMANENT MAGNETSHarold '1. Fans, Lynn, Mala, aasignor to General Electric Company, acorporation of New York No Drawing. Application October 10, 1933,

. Serial No. 692,992

Chim8.

The present invention relates to magnetic material and more particularlyto cast alloy magnets 'and to a method of making them;

It is one of the objects of the present inventlon to provide a methodwhereby permanent magnets which have desirable and substantiallyunvarying magnetic characteristics, may be readily and cheaplyfabricated.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inven-';

A preferred composition consists of about 65 parts iron. about 25 partsnickel and about 13 parts aluminum.

Infabricating the alloy the ingredients are 1 melted in any suitablecrucible and the molten mass permitted to cool. When the temperature ofthe molten metal is slightly above the melting point thereof and themetal has begun to solidify around the edges of the crucible it ispoured into a heated permanent or chillmold which has the effect ofquickly cooling. the cast metal. I prefer to heat the mold to atemperature a few hundred degrees above room temperature 1. e. about 500to 600 0. prior to pouring. The-casting may be If the casting is made ina sand mold the metal.

is poured into the mold after the metal has begun to solidify around theedges of the crucible. As soon as the surface of the casting hassolidified in the mold the casting is quickly cooledor quenched bysprinkling with water. The sprinkling preferably should be startedbefore the casting is removed from the sand. If desired, when thecasting has cooled to a temperature at which it is strong enough tosupport its own weight when seized with tongs, it may be removed fromthe mold and quenched by immersing in a suitable cooling medium such aswater. It is preferable to cool the sand castings in an air blast or bysprinkling since the castings have a tendency to crack when immersed ina cooling fluid.

By pouring the molten metal at a relatively low temperature, 1. e. afterit has begun to solidify around the edges of the crucible or slightlyprior thereto, I obtain castings having an equiaxed crystal structure.Such castings have a fairly high tensile strength. While satisfactorycastings may be made in both sand and chill molds,

it will be found thatthe chill mold in general gives more uniformresults.

Permanent mold castings of the present alloy have been made as indicatedabove which have a coercive force of about 460 and a residual of about6000. Sand mold castings of the alloy which have been quickly cooled bysprinkling or immersing in cooling fluid such as water have a coerciveforce of about 380 to 445 and a residual of about 7000 to 7600.- Sandmold castings cooled slowly in sand have a coercive force of about 325to 355 and a residual of about 4300 to 5000.

The permanent mold employed may be made of any suitable material suchassteel. Very satisfactory results however have been obtained byconstructing the permanent mold of the same alloy as the cast magnets.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is: a

1-. The method of making a permanent magnet consisting substantially ofabout 6% to 15% aluminum and to 30% nickel and the remainder iron, whichcomprises melting the ingredients of the alloy, cooling the alloy to apoint only slightly above its melting point, pouring the molten metalinto a mold and quickly cooling the cast metal.

2. The method of making a permanent magnet consisting substantially ofabout 6% to 15% aluminum and 20% to 30% nickel and the remainder iron,which comprises melting the in- 'gredients of the alloy, and'pouring themolten metal, after it has begun to solidify slightly, into a permanentmold heated to a temperature a few hundred degrees above roomtemperature.

3. The method of making a permanent magnet consisting of about 6% to 15%aluminum and 20% to 30% nickel and the remainder iron, whichcomprisesmelting the ingredients of the alloy,

pouring the molten metal, after it has begun to solidify slightly, intoa permanent mold heated to a temperature of about 500 C. to 600 C.

4. The method of making a permanent magnet consisting substantially ofabout 6% to 15% aluminum and 20% to 30% nickel and the remainder iron,which comprises melting the ingredients of the alloy, and pouring themolten metal while at a temperature only slightly above 1 its meltingpoint into a permanent mold heated toa temperature a few hundred degreesabove room temperature.

5. The method of making a permanent magnet consisting of about 6% to 15%aluminum and 20% to 30% nickel and the remainder iron, which comprisesmelting the ingredients of the alloy, pouring the molten metal while ata temperature only slightly above its melting point into a permanentmold heated to a temperature of about 500 C. to 600 C.

HAROLD T. FAUS.

